Administrator Guide

Glossary of terms
The following table lists definitions of the terms used in ME4 Series publications:
Table 43. Glossary of ME4 Series terms
Term Definition
2U12 An enclosure that is two rack units in height and can contain 12 disks.
2U24 An enclosure that is two rack units in height and can contain 24 disks.
5U84 An enclosure that is five rack units in height and can contain 84 disks.
AES Advanced Encryption Standard.
AFA All-flash array. A storage system that uses only SSDs, without tiering.
all-flash array See also AFA.
allocated page A page of virtual pool space that has been allocated to a volume to store data.
allocation rate The rate, in pages per minute, at which a virtual pool is allocating pages to its volumes because they
need more space to store data.
ALUA Asymmetric Logical Unit Access.
array See storage system.
ASC/ASCQ Additional Sense Code/Additional Sense Code Qualifier. Information on sense data returned by a SCSI
device.
automated tiered storage A virtual-storage feature that automatically uses the appropriate tier of disks to store data based on
how frequently the data is accessed. This enables higher-cost, higher-speed disks to be used only for
frequently needed data, while infrequently needed data can reside in lower-cost, lower-speed disks.
auto-write-through See AWT
available disk A disk that is not a member of a disk group, is not configured as a spare, and is not in the leftover
state. It is available to be configured as a part of a disk group or as a spare. See also compatible disk,
dedicated spare, dynamic spare, global spare.
AWT Auto-write-through. A setting that specifies when the RAID controller cache mode automatically
changes from write-back to write-through
base volume A virtual volume that is not a snapshot of any other volume, and is the root of a snapshot tree.
canister See IOM.
CAPI Configuration Application Programming Interface. A proprietary protocol used for communication
between the Storage Controller and the Management Controller in a controller module. CAPI is always
enabled.
CHAP Challenge-Handshake Authentication Protocol.
chassis The sheet metal housing of an enclosure.
child volume The snapshot of a parent volume in a snapshot tree. See parent volume.
chunk size The amount of contiguous data that is written to a disk group member before moving to the next
member of the disk group.
CIM Common Information
Model
The data model for WBEM. It provides a common definition of management information for systems,
networks, applications and services, and allows for vendor extensions.
CIMOM Common Information
Model Object Manager
A component in CIM that handles the interactions between management applications and providers.
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172 Glossary of terms